The 50/30/20 rule for your first budget

Step 1: Find your real number

Not your gross salary. The number that actually lands in your account, after ISR, IMSS, and anything else your employer withholds — your take-home pay. If you’re freelancing or selling something, use the average of your last three months, and use the lowest of the three if the months vary a lot.

If you get an aguinaldo, a bonus, or vacation pay, leave them out of the monthly plan entirely. Budgeting with money that arrives once a year is how you end up short in March.

Step 2: Write down one month of spending, honestly

Before deciding what you should spend, you need to see what you do spend. Open your banking app and go through the last 30 days. Everything: rent, groceries, transport, the taquería, subscriptions you forgot about, the OXXO run.

This step is uncomfortable and it’s the one people skip. Don’t. Almost everyone discovers between one and three thousand pesos a month going somewhere they couldn’t have named. That discovery is the whole point.

Step 3: Split it into three buckets

The 50/30/20 rule is the easiest starting point for a budget:

• 50% needs. Rent, food, transport, utilities, phone plan, minimum debt payments. Things that break your life if you stop paying them.
• 30% wants. Eating out, streaming, clothes, going out, travel. Not guilt — just the part that’s optional.
• 20% future. Emergency fund first, then paying off expensive debt, then investing.

If you live in Mexico City or Monterrey and rent, your needs will blow past 50%. That doesn’t mean the rule failed. It means your fixed costs are high, and the honest move is to cut from wants for now instead of pretending the numbers work.

Step 4: Build the emergency fund before anything else

Three to six months of essential expenses — your emergency fund — in something you can withdraw from within a day or two. Not in the same account you spend from, because it’ll disappear. Not locked into something you can’t touch for a year either.

This isn’t the exciting part, and it’s the part that decides whether one bad month turns into debt at 60% annual interest. A stable Cetes or money-market fund through a regulated brokerage is a common place people park it — the point is that it’s boring, liquid, and separate.

Step 5: Automate the part you’ll forget

The day your pay lands, move your savings out. Same day, automatically if your bank allows it. Every peso that stays in your checking account is a peso your brain treats as spendable, no matter what the spreadsheet says.

This single change does more than any amount of willpower. You’re not fighting temptation for 30 days — you’re making one decision once.

Step 6: Review monthly, adjust quarterly

Once a month, take fifteen minutes and compare plan to reality. You’re not grading yourself — you’re checking whether the plan matches your life. If you blew past the food budget three months in a row, the budget is wrong, not you.

Change the percentages every three months if you need to. A budget is a working document, not a promise.

The common failure

People build a perfect, aggressive budget: 40% savings, no eating out, no fun. It works for three weeks, one bad weekend breaks it, and they quit the whole thing. A budget you’ll actually follow at 10% savings beats a perfect one you abandon in February.

Start with numbers you can hit. Raise them when hitting them gets easy.